Play YouTube videos in background?

Is there any app to play YouTube videos/music in the background? I know about the new music key Google is releasing, but you have to subscribe to it. This app I am looking for can be an apk on some website or an app on the Play Store, but I'm pretty sure it won't be on the Play Store due to the API Terms of Service for Youtube/Google not allowing YouTube videos and other apps on the Play Store to play in the background.

Is there any app to play YouTube videos/music in the background? I know about the new music key Google is releasing, but you have to subscribe to it. This app I am looking for can be an apk on some website or an app on the Play Store, but I'm pretty sure it won't be on the Play Store due to the API Terms of Service for Youtube/Google not allowing YouTube videos and other apps on the Play Store to play in the background.